Blood: fibrinolysis: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Blood: fibrinolysis

Sample item

A 28-year-old woman with heavy menstrual bleeding is given tranexamic acid. Through which mechanism does it reduce bleeding?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Blocks lysine-binding sites on plasminogen, preventing its binding to fibrin

Plasminogen binds fibrin through lysine-binding sites and is converted to plasmin by tissue plasminogen activator. Tranexamic acid is a lysine analogue that occupies these sites, so clots are protected from premature lysis. It is used in menorrhagia, postpartum haemorrhage and trauma.

Option by option

  • A. Enhances antithrombin activity

    Antithrombin enhancement is the action of heparin, an anticoagulant.

  • B. Inhibits vitamin K epoxide reductase

    Vitamin K epoxide reductase inhibition is the action of warfarin.

  • C. Blocks lysine-binding sites on plasminogen, preventing its binding to fibrin (correct)

    Correct. It is an antifibrinolytic acting at plasminogen lysine-binding sites.

  • D. Inhibits factor Xa directly

    Direct factor Xa inhibition is the action of rivaroxaban and apixaban, which prevent clotting.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Blocks lysine-binding sites on plasminogen, preventing its binding to fibrin. Plasminogen binds fibrin through lysine-binding sites and is converted to plasmin by tissue plasminogen activator.

Why is "Enhances antithrombin activity" not the answer?

Antithrombin enhancement is the action of heparin, an anticoagulant.

Why is "Inhibits vitamin K epoxide reductase" not the answer?

Vitamin K epoxide reductase inhibition is the action of warfarin.

Why is "Inhibits factor Xa directly" not the answer?

Direct factor Xa inhibition is the action of rivaroxaban and apixaban, which prevent clotting.

What concept does this question test?

It tests Blood: fibrinolysis in Physiology. Tranexamic acid is a lysine analogue that occupies these sites, so clots are protected from premature lysis. It is used in menorrhagia, postpartum haemorrhage and trauma.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Blood: fibrinolysis?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.